Polyurethane foam and method for manufacturing the same

Abstract

The present invention provides a polyurethane foam with excellent moldability and a method for producing the same, by controlling the progress of the polyurethane foaming reaction. [Solution] The polyurethane foam is obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst. The catalyst has fully coated particles in which the catalyst component is covered by a coating material and the catalyst component is not exposed on the surface, and the content of the catalyst component in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is taken as 100% by mass. The method for producing the polyurethane foam includes a granulation step of stirring a mother particle as a catalyst component and a coating material to produce fully coated particles containing 60% by mass or more of the catalyst component, a composition preparation step of preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing the fully coated particles, and a foam curing step of foaming and curing the foamed urethane resin composition.

Description

Technical Field

[0001] The present disclosure relates to a polyurethane foam suitable for sound-absorbing materials and vibration-damping members used in vehicles, buildings, etc., and a method for producing the same.

Background Art

[0002] In vehicles such as automobiles, sound-absorbing materials, vibration-damping members, etc. are arranged at parts that are the sources of vibration and noise to reduce the transmission of vibration and the diffusion of noise. For sound-absorbing materials and vibration-damping members, foams such as polyurethane foam with low weight, high sound insulation, and high vibration absorption are used. Polyurethane foam is produced, for example, as described in Patent Document 1, by injecting a raw material (foamed urethane resin composition) having an isocyanate component, a polyol component, a catalyst, a foaming agent, etc. into a molding die and foaming and curing it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The reaction that forms polyurethane foam consists of two parts: a foaming reaction and a curing reaction (resinization reaction that forms urethane bonds) (hereinafter, these may be collectively referred to as the "foaming urethane reaction"). The catalyst plays a significant role in the progress of the foaming urethane reaction. To increase productivity, a high reaction rate is desirable, and normally, when the foaming urethane resin composition raw material is injected into the mold, the foaming and curing reactions proceed immediately. However, if the foaming reaction proceeds too quickly, the mold may not be able to keep up. Also, if the curing reaction proceeds too quickly, insufficient foaming may occur, or the curing reaction may be completed before the raw material reaches the corners and details of the mold, potentially resulting in molding defects.

[0005] For example, Patent Document 2 describes a method for using a catalyst by encapsulating it. By encapsulating a catalyst and releasing it at a desired temperature, the progress of the reaction in which the catalyst acts can be controlled. Patent Document 2 describes a method for encapsulating a catalyst in which the catalyst is dispersed or dissolved in an encapsulating agent such as a thermoplastic resin, catalyst droplets are formed, and then cooled to solidify them. In addition to this, a conventional method of coating the surface of core particles (mother particles) with a coating material such as a resin has been known, which involves mixing the mother particles with the coating material and then spray-drying or grinding them.

[0006] However, with conventional methods, the catalyst is often not completely coated, and a portion of the catalyst is exposed on the surface. When such partially coated particles are used as a catalyst, the exposed catalyst initiates curing reactions, and the heat generated during these reactions melts the coating material, such as thermoplastic resin, releasing the catalyst. As a result, the initial reaction delaying effect of the coating is not sufficiently obtained. Consequently, curing defects cannot be adequately suppressed, and moldability is reduced. Furthermore, when using the spray drying method, if the amount of catalyst used as the mother particle is increased, the resulting particles will aggregate, forcing a reduction in the amount of catalyst contained in each particle. Consequently, the catalyst's inherent reaction-promoting effect is also reduced.

[0007] This disclosure has been made in view of the above circumstances, and aims to provide a polyurethane foam with excellent moldability and a method for producing the same by controlling the progress of the urethane foaming reaction. [Means for solving the problem]

[0008] (1) In order to solve the above problems, the polyurethane foam of the present disclosure is a polyurethane foam obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst, wherein the catalyst has fully coated particles in which the catalyst component is covered with a coating material and the catalyst component is not exposed on the surface, and the content of the catalyst component in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

[0009] The polyurethane foam of this disclosure is manufactured from a foamed urethane resin composition in which at least a portion of the catalyst is fully coated particles. Fully coated particles are coated catalyst particles in which the catalyst component is covered with a coating material, and the catalyst component is not exposed on the surface. In fully coated particles, when a predetermined temperature is reached, the coating material changes, such as melting, and the catalyst component is released. In other words, fully coated particles do not act as a catalyst until they reach the temperature at which the state of the coating material changes. By thus imparting temperature dependence to the catalyst, the timing of catalyst action can be delayed, and the foaming reaction and curing reaction can be carried out in a well-balanced manner. As a result, the foamed urethane resin composition can be spread to the corners and details of the mold before the curing reaction progresses and viscosity increases. This suppresses the occurrence of insufficient foaming and insufficient filling, and enables the realization of a polyurethane foam with excellent moldability. Furthermore, in fully coated particles, the catalyst component is not exposed on the surface. Therefore, the initial reaction delay effect due to the coating can be reliably obtained. In addition, 60% by mass or more of the fully coated particles is the catalyst component. Because it contains a relatively large amount of catalytic components, fully coated particles can fully exhibit the catalyst's inherent reaction-promoting effect, even in a coated form.

[0010] (2) In the above configuration, the solubility parameter value of the coating material may be set to 10 or higher. The solubility parameter (SP value) of the polyol component, which is the main component of the foamed urethane resin composition, is 8.6. With this configuration, since the SP value of the coating material is not too close to the SP value of the polyol component, the coating material does not easily dissolve in the polyol component. Therefore, the behavior of the coating material with respect to temperature, such as melting at a predetermined temperature, is not easily inhibited.

[0011] (3) In any of the above configurations, the coating material may be one or more selected from thermoplastic resin, wax, fatty acid, and ester compound. This configuration makes it easier to produce fully coated particles in which the coating material melts at a desired temperature.

[0012] (4) In the configuration of (3) above, the glass transition temperature of the thermoplastic resin may be 40°C or more and 70°C or less, and the melting points of the wax, the fatty acid, and the ester compound may be 40°C or more and 70°C or less. With this configuration, the coating material can be melted and the catalyst component released at the temperature at which the foamed urethane resin composition is foamed and cured (the molding temperature of the polyurethane foam).

[0013] (5) In the configuration of (3) or (4) above, the thermoplastic resin may be composed of polyvinyl butyrate, polyethylene oxide, and polystyrene. The SP value of these resins is 10 or more, and the glass transition temperature is 40°C to 70°C. Therefore, they are poorly soluble in the polyol component and can be melted at the molding temperature of polyurethane foam.

[0014] (6) In any of the above configurations, the catalyst component contained in the overall coated particles may be one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

[0015] (7) In any of the above configurations, the fully coated particle may have a core-shell structure comprising a coating layer forming the outermost layer of the particle and a catalyst component layer disposed inside the coating layer. This configuration makes it easier to produce fully coated particles in which the catalyst component content is 60% by mass or more and the catalyst component is not exposed on the surface.

[0016] (8) In the configuration of (7) above, the average particle size of the overall coating particles having a core-shell structure may be 5 μm or more and 800 μm or less, and the thickness of the coating layer may be 0.01 μm or more and 100 μm or less. With this configuration, the size of the overall coating particles becomes appropriate, the dispersibility in the foamed urethane resin composition is good, and polyurethane foam can be manufactured with good moldability.

[0017] (9) A method for producing polyurethane foam according to the present disclosure is one form of a method for producing polyurethane foam having any of the configurations of (1) to (8) above, comprising: a granulation step of stirring mother particles as a catalyst component and a coating material to produce fully coated particles in which the mother particles are coated with the coating material and the mother particles are not exposed on the surface; a composition preparation step of preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing the fully coated particles; and a foam curing step of foaming and curing the foamed urethane resin composition, wherein the content of the mother particles in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

[0018] According to the manufacturing method of this disclosure, the initial reaction delay effect of the overall-coating particles allows for a balanced progression of the foaming and curing reactions, enabling the production of polyurethane foam with good moldability. For example, before the curing reaction progresses and viscosity increases, the foamed urethane resin composition can reach even the corners and fine details of the mold, thereby suppressing insufficient foaming and insufficient filling, and enabling the production of products with complex shapes with good moldability. [Effects of the Invention]

[0019] The polyurethane foam of the present disclosure is produced from a urethane resin foam composition using whole-coated particles in which the catalyst component is not exposed on the surface. Due to the initial reaction delay effect, the foaming reaction and the curing reaction proceed in a well-balanced manner, resulting in excellent moldability. According to the method for producing the polyurethane foam of the present disclosure, the initial reaction delay effect by the whole-coated particles enables the foaming reaction and the curing reaction to proceed in a well-balanced manner, and the polyurethane foam can be produced with good moldability.

Mode for Carrying Out the Invention

[0020] Hereinafter, embodiments of the polyurethane foam and the method for producing the same according to the present disclosure will be described. Note that the embodiments are not limited to the following forms, and various modified forms and improved forms that can be made by those skilled in the art can be implemented.

[0021] <Polyurethane Foam> The polyurethane foam of the present disclosure is obtained by foaming and curing a urethane resin foam composition having an isocyanate component, a polyol component, and a catalyst.

[0022] [Isocyanate Component] The isocyanate component is not particularly limited as long as it forms a urethane bond by reacting with the polyol component. For example, it may be appropriately selected from tolylene diisocyanate (TDI), phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate (NDI), and derivatives thereof. Examples of the derivatives include prepolymers obtained by reacting isocyanate with polyol, modified polyisocyanates, polymeric MDI (polynuclear) having three or more isocyanate groups and benzene rings in one molecule, and the like.

[0023] [Polyol Component] As the polyol component, it may be appropriately selected from polyhydric hydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, etc.

[0024] For example, it is desirable to use a polyether polyol as the main component. The "main component" is a component that occupies 60% by mass or more when the total of the polyol component is 100% by mass. That is, as the polyol component, only a polyether polyol may be used, or a polyether polyol may be used as the main component and other polyols may be appropriately combined and used. For example, from the viewpoint of improving moldability, it is desirable to use a polyester polyol in combination. Also, even when only a polyether polyol is used, a plurality of types having different functional group numbers, molecular weights, compatibilities, etc. may be combined and used.

[0025] [Catalyst] The catalyst includes coated catalyst particles in which the catalyst component is coated with a coating material and includes entirely coated particles in which the catalyst component is not exposed on the surface. The catalyst may include partially coated particles in which a part of the catalyst component is exposed on the surface as the coated catalyst particles. The catalyst may also include an uncoated catalyst component. The mass ratio of the entirely coated particles in the whole catalyst is preferably 50% by mass or more when the mass of the whole catalyst is 100% by mass. 60% by mass or more, and more preferably 70% by mass or more.

[0026] The content of the catalyst component in the entirely coated particles is set to 60% by mass or more when the mass of the entirely coated particles is 100% by mass from the viewpoint of exerting the original reaction promoting effect of the catalyst. It is more preferable to set it to 65% by mass or more, 70% by mass or more. On the other hand, since a predetermined amount of the coating material is also required so as not to expose the catalyst component on the surface, the content of the catalyst component is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0027] The coating material constituting coated catalyst particles, such as fully coated particles, can be any material that changes state at a predetermined temperature and releases catalyst components. Examples include thermoplastic resins, waxes, fatty acids, and ester compounds. One or more of these can be used. For example, from the viewpoint of being less prone to change at temperatures near room temperature and more prone to change at the molding temperature, thermoplastic resins with a glass transition temperature (Tg) of 40°C to 70°C are desirable, and waxes, fatty acids, and ester compounds with a melting point (Tm) of 40°C to 70°C are desirable. Examples of thermoplastic resins with a Tg of 40°C to 70°C include polyvinyl butyrate, polyethylene oxide, polystyrene, terpene phenol, and acrylic resin. Examples of waxes with a Tm of 40°C to 70°C include paraffin wax, microcrystalline wax, and modified polyethylene wax. Examples of fatty acids include stearic acid, behenic acid, and maleic anhydride. Examples of ester compounds include distearyl 3,3'-thiodipropionic acid and behenyl behenate.

[0028] Furthermore, it is desirable that the coating material is poorly soluble in the polyol components that come into contact with it during the preparation of the foamed urethane resin composition. For this reason, it is desirable that the SP value of the coating material be as far apart as possible from the SP value of the polyol components. For example, it is desirable that the SP value of the coating material be 10 or higher. Examples of thermoplastic resins with a Tg of 40°C to 70°C and an SP value of 10 or higher include polyvinyl butyrate, polyethylene oxide, polystyrene, terpene phenol, and acrylic resin.

[0029] Examples of catalytic components that make up coated catalyst particles, such as fully coated particles, include amine catalysts such as triethylenediamine, tetraethylenediamine, dimethylethanolamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine, as well as metal catalysts such as tin laurate and tin octanoate. Among these, it is desirable to use one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine, from the viewpoint of high catalytic activity and ease of obtaining them in powder form.

[0030] The morphology of coated catalyst particles, such as fully coated particles, may be either a sea-island structure in which the catalyst component is dispersed within the coating material, or a core-shell structure in which the catalyst component forms the core layer and the coating material forms the shell layer. The core-shell structure makes it easier to coat a relatively large amount of catalyst component without exposing it to the surface. Therefore, it is desirable for fully coated particles to have a core-shell structure having a coating material layer forming the outermost layer of the particle and a catalyst component layer arranged inside the coating material layer.

[0031] The shape of the overall coating particles is not particularly limited and may include spherical, flaky, or irregularly shaped clumps. In this specification, "spherical" is not limited to perfectly spherical shapes, but includes shapes close to spherical (approximately spherical).

[0032] The particle size of the overall coating particles is not particularly limited and can be appropriately determined considering factors such as dispersibility when preparing the foamed urethane resin composition and viscosity when mixed with the polyol component. For example, it may be several tens to several hundred μm, or even just a few μm. For instance, the average particle size of the overall coating particles can be between 5 μm and 800 μm. The overall coating particles may be used as manufactured, or they may be subjected to grinding or other processes to reduce their particle size. Reducing the particle size of the overall coating particles makes them easier to mix with the polyol component and the isocyanate component. Furthermore, when a premixed polyol is prepared by mixing the catalyst and the polyol component beforehand, and then mixed with the isocyanate component using a high-pressure jet foaming device, the limitations on nozzle diameter and other factors become less significant. For example, if the overall coating particles have a core-shell structure and an average particle size of 5 μm to 800 μm, the thickness of the coating layer should be between 0.01 μm and 100 μm. In this specification, the average particle size is the median diameter (D) determined from the volume-based particle size distribution measured by laser diffraction and scattering. 50 )

[0033] [Other ingredients] In addition to the materials mentioned above, the foamed urethane resin composition may also contain known materials used in the manufacture of polyurethane foam, such as foaming agents, chain extenders, foam stabilizers, crosslinking agents, plasticizers, flame retardants, antistatic agents, viscosity reducers, stabilizers, fillers, and colorants. Of these, water is preferred as the foaming agent. Other examples include methylene chloride, chlorofluorocarbons (CFCs), and carbon dioxide. Examples of chain extenders include ethylene glycol, diethylene glycol, propylene glycol, 3-methyl-1,5-pentanediol, and 1,9-nonanediol. Examples of foam stabilizers include polyether-modified silicone compounds and polyester-modified silicone compounds. Examples of crosslinking agents include triethanolamine and diethanolamine. Various pigments can be used as colorants, and the presence of black pigments, in particular, can improve the weather resistance and sound insulation properties of the polyurethane foam.

[0034] <Method for manufacturing polyurethane foam> One embodiment of the method for manufacturing polyurethane foam according to this disclosure comprises a granulation step, a composition preparation step, and a foaming and curing step. Each step will be described below.

[0035] [Granulation process] This process involves stirring mother particles as catalyst components with a coating material to produce fully coated particles in which the mother particles are covered with the coating material and no mother particles are exposed on the surface. The mixing ratio of mother particles to coating material should be adjusted so that the mother particle content is 60% or more of the total mass of the produced fully coated particles, with the total mass being 100% by mass. The stirring of the mother particles and coating material can be carried out using an appropriate method depending on the type of coating material, the size of the mother particles, etc. For example, it can be done by adding the mother particles to a coating material solution in which the coating material is dissolved in a solvent. Alternatively, it can be done by adding small amounts of water as a binder and the coating material to the mother particles. Alternatively, it can be done by adding water as a binder to the mother particles beforehand to wet the surface of the mother particles, and then adding the coating material. Stirring should be carried out at room temperature to about 30°C, as stirring at temperatures above 40°C may cause the catalyst components to sublimate or the coating material to melt. Although this process is for producing fully coated particles, the coated catalyst particles produced by this process may also include partially coated particles.

[0036] [Composition preparation process] This process involves preparing a foamed urethane resin composition comprising an isocyanate component, a polyol component, and a catalyst containing fully coated particles. As the catalyst, not only fully coated particles but also partially coated particles or uncoated catalyst components may be used. The components, including the catalyst, are as described in the embodiments of the polyurethane foam of this disclosure.

[0037] The foamed urethane resin composition can be prepared, for example, as follows: First, a premixed polyol is prepared by pre-mixing a polyol component with a catalyst other than the isocyanate component, a blowing agent, etc. Next, the isocyanate component is mixed into the prepared premixed polyol. The premixed polyol and the isocyanate component may be mixed by mechanical stirring with a stirring blade or the like, or by using a high-pressure jet foaming device to spray the two materials at high pressure and mix them by impact (impact stirring method). Compared to the mechanical stirring method, the impact stirring method eliminates the need for cleaning the containers that were required after each mixing, improving the yield. Therefore, manufacturing costs can be reduced.

[0038] It is desirable to blend the polyol component and the isocyanate component such that the isocyanate index (equivalent ratio of isocyanate groups to active hydrogen groups) is between 0.9 and 1.5. Furthermore, when using only fully coated particles as a catalyst, the progress of the foam urethane reaction is suppressed until the predetermined temperature is reached, allowing the foam urethane resin composition to be prepared in advance. This improves workability.

[0039] [Foaming and curing process] This step involves foaming and curing the prepared foamed urethane resin composition. For example, the prepared foamed urethane resin composition can be injected into a mold and foamed while sealed or open. The foaming should be performed at a temperature at which the state of the coating material changes, such as when the coating material melts, taking into account the glass transition point or melting point of the coating material that constitutes the overall coating particles. For example, the temperature of the foamed urethane resin composition should be between 40°C and 100°C. [Examples]

[0040] Next, the present disclosure will be described in more detail with reference to examples.

[0041] <Manufacturing of coated catalyst particles> [Granulation method] Triethylenediamine particles, the catalyst component, were placed in a stirring and mixing granulation apparatus manufactured by Powrec Co., Ltd., and coated catalyst particles were produced by adding small amounts of water and coating material as a binder while stirring at room temperature. Seven types of coated catalyst particles were produced by changing the mixing ratio of the catalyst component and coating material, and the type of coating material. The compositions of the coated catalyst particles are shown in Table 1 below (Examples 1-6, Comparative Example 6).

[0042] [Spray drying method] Coated catalyst particles were produced by spray-drying a dispersion of triethylenediamine particles (a catalyst component) and polyvinyl butyrate (a coating material) in acetone using a spray dryer manufactured by Yamato Scientific Co., Ltd. Four types of coated catalyst particles were produced by varying the mixing ratio of the catalyst component and the coating material. The compositions of the coated catalyst particles are shown in Table 1 below (Comparative Examples 2-5).

[0043] [Regarding the manufactured coated catalyst particles] Table 1 indicates cases where the yield of coated catalyst particles was 50% or higher with a circle (○), and cases where the yield of coated catalyst particles was less than 50% due to particle aggregation or other reasons with a cross (×). Only coated catalyst particles with a composition that yielded 50% or higher were used in the production of polyurethane foam (Examples 1-6, Comparative Examples 2 and 3).

[0044] In the coated catalyst particles of Examples 1 to 6, which were produced by granulation and had a yield of 50% or more, at least 50% by mass of the particles were fully coated particles in which the catalyst component was not exposed on the surface. In contrast, in the coated catalyst particles of Comparative Examples 2 and 3, which were produced by spray drying, although aggregation was less likely due to the low content of the catalyst component and the yield was 50% or more, no fully coated particles were produced, and almost all of them were partially coated particles.

[0045] <Manufacturing of polyurethane foam> First, a premix polyol was prepared by adding 1 part by mass of diethylene glycol as a chain extender, 1.5 parts by mass of water as a blowing agent, and the prepared coated catalyst particles in the amounts shown in Table 1 to 100 parts by mass of polypropylene glycol (PPG) (VORANOL® CP 6001, manufactured by DOW, with an average molecular weight of 6000 and 3 functional groups) as the polyol component and mixing. Next, an isocyanate agent having polymeric MDI (Millionate MR-200, manufactured by Tosoh Corporation) was prepared as the isocyanate component. Then, the premix polyol and the isocyanate agent were mixed and stirred so that the isocyanate index was 0.95 to prepare a foamed urethane resin composition. Immediately thereafter, the foamed urethane resin composition was poured into aluminum cups maintained at two different temperatures, 20°C and 80°C, and allowed to foam and cure with the cups open while measuring the viscosity of the foamed urethane resin composition using a tuning fork vibration viscometer (A&D Co., Ltd. "SV-100"). The curing reaction delay and reactivity were then evaluated based on the measured viscosity values ​​as follows.

[0046] (1) Delay In the change in viscosity over time when foaming and curing at 20°C, if the viscosity of the premix polyol and isocyanate agent 120 seconds after the start of stirring was less than 70 Pa·s, it was determined that the reaction delay effect due to fully coated particles was exhibited (indicated by ○ in Table 1 below). If the viscosity was 70 Pa·s or more but less than 100 Pa·s, it was determined that the reaction delay effect was small and insufficient (indicated by △ in the same table), and if the viscosity was 100 Pa·s or more, it was determined that no reaction delay effect was obtained (indicated by × in the same table).

[0047] (2) Reactivity In the viscosity change over time when foaming and curing at 80°C, if the viscosity of the premix polyol and isocyanate agent 120 seconds after the start of stirring was 100 Pa·s or higher, it was determined that the reaction-promoting effect due to fully coated particles was exhibited (indicated by ○ in Table 1 below). If the viscosity was 70 Pa·s or higher but less than 100 Pa·s, it was determined that the reaction-promoting effect was small and insufficient (indicated by △ in the same table), and if the viscosity was less than 70 Pa·s, it was determined that no reaction-promoting effect was obtained.

[0048] Table 1 summarizes the composition of the coated catalyst particles, the composition of the foamed urethane resin composition, and the evaluation results. The polyurethane foams of Examples 1 to 6 shown in Table 1 are included in the concept of polyurethane foam of this disclosure. Note that the polyurethane foam of Comparative Example 1 was manufactured using triethylenediamine particles, which are the mother particles of the coated catalyst particles, rather than the manufactured coated catalyst particles. [Table 1]

[0049] As shown in Comparative Example 1 of Table 1, when only uncoated catalyst was used, the curing reaction proceeded and viscosity increased even at 20°C, close to room temperature. In contrast, as shown in Examples 1 to 6, when 50% or more by mass of the catalyst consisted of fully coated particles, both the curing reaction retardation and reactivity were satisfactory. That is, the curing reaction was suppressed at 20°C, and the curing reaction proceeded at the molding temperature of 80°C. Furthermore, in the case of the coated catalyst particles of Comparative Examples 2 and 3, which were manufactured by the spray-drying method, almost all were partially coated particles, so using them did not have a significant reaction retardation effect. In addition, the coated catalyst particles of Comparative Examples 2 and 3 had a low catalyst component content, resulting in reduced reactivity. [Industrial applicability]

[0050] The polyurethane foam disclosed herein is suitable for use as a sound-absorbing material, vibration-damping material, etc., in vehicles, buildings, and the like.

Claims

1. A polyurethane foam obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst, The catalyst has fully coated particles in which the catalytic component is covered by a coating material and the catalytic component is not exposed on the surface. A polyurethane foam characterized in that the content of the catalyst component in the overall coated particles is 60% by mass or more, when the total mass of the overall coated particles is taken as 100% by mass.

2. The polyurethane foam according to claim 1, wherein the solubility parameter value of the coating material is 10 or more.

3. The polyurethane foam according to claim 1, wherein the coating material is one or more selected from thermoplastic resins, waxes, fatty acids, and ester compounds.

4. The polyurethane foam according to claim 3, wherein the glass transition temperature of the thermoplastic resin is 40°C or higher and 70°C or lower, and the melting points of the wax, the fatty acid, and the ester compound are 40°C or higher and 70°C or lower.

5. The polyurethane foam according to claim 3, wherein the thermoplastic resin comprises polyvinyl butyrate, polyethylene oxide, and polystyrene.

6. The polyurethane foam according to claim 1, wherein the catalyst component contained in the overall coated particles is one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

7. The polyurethane foam according to claim 1, wherein the overall coated particles have a core-shell structure comprising a coating layer forming the outermost layer of the particles and a catalyst component layer disposed inside the coating layer.

8. The average particle diameter of the overall coated particles having a core-shell structure is 5 μm or more and 800 μm or less. The polyurethane foam according to claim 7, wherein the thickness of the coating layer is 0.01 μm or more and 100 μm or less.

9. A granulation step involves stirring mother particles as catalyst components and a coating material to produce fully coated particles in which the mother particles are covered by the coating material and the mother particles are not exposed on the surface. A composition preparation step for preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing the overall coating particles, A foam curing step for foaming and curing the foamed urethane resin composition, It has, A method for producing polyurethane foam, characterized in that the content of the mother particles in the overall coated particles is 60% by mass or more when the mass of the overall coated particles is taken as 100% by mass.

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